Invasion and replication of Brucella abortus in three different trophoblastic cell lines

Kinetics of Placental Infection by Different Smooth Brucella Strains in Mice

Abortion and reproductive failures induced by Brucella are the main symptoms of animal brucellosis. Laboratory animal models are essential tools of research to study the Brucella pathogenesis before experimentation in natural hosts. To extend the existing knowledge, we studied B. melitensis 16M (virulent) and Rev1 (attenuated) as well as B. suis bv2 infections in pregnant mice. Here, we report new information about kinetics of infection (in spleens, blood, placentas, vaginal shedding, and foetuses), serum cytokine profiles, and histopathological features in placentas and the litter throughout mice pregnancy. Both B. melitensis strains showed a marked placental tropism and reduced viability of pups (mainly in 16M infections), which was preceded by an intense Th1-immune response during placental development. In contrast, B. suis bv2 displayed lower placental tropism, mild proinflammatory immune response, and scarce bacterial transmission to the litter, thus allowing foetal viability. Overall, our studies revealed three different smooth Brucella patterns of placental and foetal pathogenesis in mice, providing a useful animal model for experimental brucellosis.

Erythritol Availability in Bovine, Murine and Human Models Highlights a Potential Role for the Host Aldose Reductase during Brucella Infection

Erythritol is the preferential carbon source for most brucellae, a group of facultative intracellular bacteria that cause a worldwide zoonosis. Since this polyol is abundant in genital organs of ruminants and swine, it is widely accepted that erythritol accounts at least in part for the characteristic genital tropism of brucellae. Nevertheless, proof of erythritol availability and essentiality during Brucella intracellular multiplication has remained elusive. To investigate this relationship, we compared ΔeryH (erythritol-sensitive and thus predicted to be attenuated if erythritol is present), ΔeryA (erythritol-tolerant but showing reduced growth if erythritol is a crucial nutrient) and wild type B. abortus in various infection models. This reporting system indicated that erythritol was available but not required for B. abortus multiplication in bovine trophoblasts. However, mice and humans have been considered to lack erythritol, and we found that it was available but not required for B. abortus multiplication in human and murine trophoblastic and macrophage-like cells, and in mouse spleen and conceptus (fetus, placenta and envelopes). Using this animal model, we found that B. abortus infected cells and tissues contained aldose reductase, an enzyme that can account for the production of erythritol from pentose cycle precursors.

Excretion of Brucella abortus vaccine B19 strain during a reproductive cycle in dairy cows

This paper aimed to determine the excretion period of B19 vaccine strain during a complete reproductive cycle (from estrus synchronization, artificial insemination, pregnancy and until 30 days after parturition) of dairy cows from 3 to 9 years old that were previously vaccinated from 3 to 8 months. Three groups were monitored with monthly milk and urine collection during 12 months: G1 with seven cows from 3 to 4 years old; G2 with three cows from 5 to 6 years old; and G3 with four cows from 7 to 9 years old. Urine and milk samples were submitted to bacteriological culture and urine and PCR reactions for detection of Brucella spp. and PCR-multiplex for B19 strain identification. Ring test (RT) was also performed in the milk samples, and serum samples were tested by buffered acidified plate antigen test (BAPA). All animals were serologically negative at BAPA and Brucella spp. was not isolated from both urine and milk samples. RT revealed 13/210 (6.2%) positive milk samples. PCR reactions detected DNA of Brucella spp. in 86/420 (20.5%) samples. In urine it was found a significantly higher frequency (35.2%; 74/210) than in milk (5.7%; 12/210), more frequently from the estrus to 150 days of pregnancy and after parturition (6.7%; 10/150), and from 150 days of pregnancy to parturition (3.4%; 2/60), and they were all identified as B19 strain. In three groups, intermittent excretion of B19 strain was detected mainly in urine samples, which confirmed its multiplication and persistence in cows for until 9 years.

The pathology of brucellosis reflects the outcome of the battle between the host genome and the Brucella genome

The successful co-existence of each Brucella spp. with its preferred host is the outcome of ancient co-evolutionary relationships and selection pressures that often result in a stalemate where the pathogen has evolved to survive within the biological systems of the host, and the host has evolved innate and acquired immune systems which allow controlled survival of infection by the pathogen, ultimately supporting the survival of the host-pathogen system. In general, Brucella spp. have evolved a similar fundamental pathogenesis of facultative intracellular parasitism though the predominant route of natural exposure varies from oropharynx to genital tract, as does the preferred tissue and cellular tropism, e.g. non-professional placental trophoblasts, fetal lung, professional macrophages of reticulendothelial system, and the male and female reproductive tracts. The morphogenesis of the pyogranulomatous lesions stimulated by Brucella reflects the nature of the persistent parasitism, i.e. genome versus genome. The question is, how can this perplexing array of survival mechanisms be unraveled? Fortunately, the integration of real-time image analysis, cell biology, genome-wide analysis, proteomics and bioinformatics holds the most promise ever for the global analysis of the Brucella infectious process and the host:pathogen interface leading to a clearer understanding of the interactions of these biological systems. These discoveries will be expected to provide a frameshift in rationales for interrupting and/or controlling brucellosis at host and/or pathogen levels.

Immunohistochemical detection of Brucella abortus antigens in tissues from aborted bovine fetuses using a commercially available polyclonal antibody

A commercially available polyclonal antibody and an avidin-biotin-peroxidase immunohistochemical technique were used to detect Brucella abortus antigens in formalin-fixed, paraffin-embedded tissues of lung and liver from 20 aborted bovine fetuses. Thirteen fetuses were obtained from farms with a previous history of brucellosis, and 7 were collected from farms without a history of brucellosis. Among the 13 aborted bovine fetuses obtained from farms with a history of brucellosis, immunoreactivity to B. abortus was detected in lung (9 fetuses) and in liver (1 fetus), whereas Brucella was cultured from abomasal contents in 9 fetuses (8 were immunohistochemically positive). In addition, 11 dams of these 13 aborted bovine fetuses had antibodies to Brucella. Brucella abortus was not detected by immunohistochemistry in the 7 aborted bovine fetuses collected from farms without a history of brucellosis. Bacteriologic culture and serologic tests were also negative for Brucella. The results of this study revealed that the immunohistochemical technique was sufficiently sensitive for detecting B. abortus antigens in formalin-fixed lung tissues from naturally aborted bovine fetuses. Although additional studies are necessary to rule out cross-reaction of the polyclonal antibody with other microorganisms that cause bovine abortion, this immunohistochemical technique could be a complementary tool to serology and bacteriology for the diagnosis of brucellosis.